Patent application title: Ball and Socket Joint for a Motor Vehicle

Abstract:

A ball and socket joint for a motor vehicle is provided with a joint
housing (2), with a ball pivot (3), which is mounted rotatably and
pivotably in same and which is in contact with the joint housing (2) or
with a ball shell (7) arranged between this and the ball pivot (5). The
ball and socket joint has an angle measuring device (20, 21), by which
the angle of the ball pivot (5) relative to the joint housing (2) can be
detected. At least two temperature sensors (15, 16) are arranged at
spaced locations from one another in or on the joint housing (2).

Claims:

1-15. (canceled)

16. A ball and socket joint for a motor vehicle, ball and socket joint
comprising:a joint housing;a ball pivot mounted rotatably and pivotably
in said joint housing, said ball pivot being in contact with said joint
housing or with a ball shell arranged between said joint housing and said
ball pivot;an angle measuring device for detecting an angle of said ball
pivot relative to said joint housing; andat least two temperature sensors
arranged at spaced locations from one another in or on said joint
housing.

17. A ball and socket joint in accordance with claim 16, wherein a
frictional heat flux is generated by a motion of the ball pivot in
relation to said joint housing, and said temperature sensors are seated
in different positions in said frictional heat flux.

18. A ball and socket joint in accordance with claim 16, wherein said ball
pivot has a pin and a joint ball connected to same, wherein said two
temperature sensors are arranged at different distances from a center of
said joint ball.

19. A ball and socket joint in accordance claim 16, further comprising a
plate or printed circuit board arranged in or on said joint housing
wherein said two temperature sensors are seated on mutually opposite
sides of said plate or printed circuit board.

20. A ball and socket joint in accordance with claim 19, wherein said
joint housing has a bottom and an opening located opposite said bottom,
said ball pivot extending through t said opening, said plate or printed
circuit board being arranged in the area of said bottom.

21. A ball and socket joint in accordance with claim 20, further
comprising a cover wherein said bottom has an opening closed by said
cover, wherein said cover has said plate or printed circuit board or
comprises said plate or printed circuit board.

22. A ball and socket joint in accordance claim 16, wherein said angle
measuring device is arranged in said ball and socket joint housing.

23. A ball and socket joint in accordance claim 16, further comprising a
force sensor, wherein a force exerted by said ball pivot on said joint
housing or on said ball shell is determined by said force sensor.

24. A ball and socket joint in accordance with claim 23, wherein said
force sensor is arranged in said ball and socket joint housing.

25. A ball and socket joint in accordance claim 16, further comprising
analyzing means for determining a wear indicator characterizing wear of
said ball and socket joint, wherein said two temperature sensors and said
angle measuring device are connected to said analyzing means.

26. A ball and socket joint in accordance with claim 25, wherein said
analyzing means has a differentiator connected to said angle measuring
device, a difference former connected to said two temperature sensors and
a calculating unit arranged downstream of said differentiator and said
difference former.

27. A ball and socket joint in accordance with claim 25, wherein said
analyzing means is formed by at least one said digital computer.

28. A process for determining a wear indicator characterizing wear of a
ball and socket joint, the process comprising the steps of:providing a
joint housing;providing a ball pivot mounted rotatably and pivotably in
said joint housing, said ball pivot being in contact with said joint
housing or with a ball shell arranged between said joint housing and said
ball pivot;providing an angle measuring device for detecting an angle of
said ball pivot relative to said joint housing; andarranging at least two
temperature sensors at spaced locations from one another in or on said
joint housingdetermining angle data by consecutive measurement of said
angle between said ball pivot and said joint housing;determining a
velocity by differentiating the angle data over time;measuring
temperatures at least two different sites in or on said ball and socket
joint; anddetermining the wear indicator on the basis of said velocity
and said temperatures.

29. A process in accordance with claim 28, wherein said wear indicator is
multiplied by a joint-specific constant and divided by a radius of a
joint ball of said ball pivot.

30. A process in accordance with claim 28, wherein a force exerted by said
ball pivot on said joint housing or on a ball shell arranged between said
ball pivot and said joint housing is measured and the wear indicator is
additionally determined on the basis of said force.

31. A ball and socket joint for a motor vehicle, ball and socket joint
comprising:a joint housing with a bottom and an opening located opposite
said bottom;a ball pivot including a joint ball and a pin extending
through said opening, said joint ball being mounted rotatably and
pivotably in said joint housing;a ball shell arranged between said joint
housing and said ball pivot;an angle measuring device for detecting an
angle of said ball pivot relative to said joint housing;a first
temperature sensor in or on said joint housing; anda second temperature
sensor arranged in or on said joint housing at spaced location from said
first temperature sensor wherein said two temperature sensors are
arranged at different distances from a center of said joint ball, wherein
a frictional heat flux is generated by a motion of the ball pivot in
relation at least one of said ball shell and said joint housing, and said
temperature sensors are seated in different positions in said frictional
heat flux.

32. A ball and socket joint in accordance claim 31, further comprising
further comprising:a cover wherein said bottom has an opening closed by
said cover, wherein said cover has a plate or printed circuit board or
comprises a plate or printed circuit board and wherein said two
temperature sensors are seated on mutually opposite sides of said plate
or printed circuit board.

33. A ball and socket joint in accordance claim 31, further comprising a
force sensor, wherein a force exerted by said ball pivot on said joint
housing or on said ball shell is determined by said force sensor said
force sensor being arranged in said ball and socket joint housing.

34. A ball and socket joint in accordance claim 31, further comprising
analyzing means for determining a wear indicator characterizing wear of
said ball and socket joint, wherein said two temperature sensors and said
angle measuring device are connected to said analyzing means.

35. A ball and socket joint in accordance with claim 34, wherein said
analyzing means has a differentiator connected to said angle measuring
device, a difference former connected to said two temperature sensors and
a calculating unit arranged downstream of said differentiator and said
difference former.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

[0001]This application is a United States National Phase application of
International Application PCT/DE 2006/001150 and claims the benefit of
priority under 35 U.S.C. § 119 of German Patent Application DE 10
2005 034 150.0 filed Jul. 19, 2005, the entire contents of which are
incorporated herein by reference.

FIELD OF THE INVENTION

[0002]The present invention pertains to a ball and socket joint for a
motor vehicle, with a joint housing; with a ball pivot, which is mounted
rotatably and pivotably in same and which is in contact with the joint
housing or with a ball shell arranged between this and the ball pivot;
and with an angle measuring device, by means of which the angle of the
ball pivot relative to the joint housing can be detected. The present
invention pertains, furthermore, to a process for determining a wear
indicator characterizing the wear of a ball and socket joint.

BACKGROUND OF THE INVENTION

[0003]Thermal and/or mechanical overloading of a ball and socket joint
leads to a change in the "tribological conditions" in the joint, and the
change may be due, e.g., to hardening of the lubricating grease or to
wear of the ball shell. This overloading cannot be measured online in the
measuring device or on the test bench. Only the measurement of the
elasticity of the joints on a test bench is possible. It is only in case
of very great wear of the ball and socket joint that a free clearance
develops in the joint and "unbuttoning" of the joint develops later. It
is not yet possible to determine a premature wear in the motor vehicle.

SUMMARY OF THE INVENTION

[0004]The object of the present invention is to perfect a ball and socket
joint of the type mentioned above such that a wear indicator
characterizing the wear of the ball and socket joint can be determined.

[0005]The ball and socket joint according to the present invention for a
motor vehicle has a joint housing; a ball pivot, which is mounted
rotatably and pivotably in this and which is in contact with the joint
housing or with a ball shell arranged between this and the ball pivot;
and an angle measuring device, by means of which the angle of the ball
pivot relative to the joint housing can be detected, wherein at least two
temperature sensors are arranged at mutually spaced locations from one
another in or on the joint housing. The ball pivot has especially a pin
and a joint ball, which is connected to same and which is preferably
lubricated with a lubricant introduced into the joint housing, e.g.,
grease. Furthermore, the ball shell may be a one-part or multipart shell.

[0006]During a motion of the ball pivot relative to the joint housing,
heat is generated by friction, and this heat leads to a heat flux in the
joint. It was found that the quotient of the difference between
temperature values detected at two different sites and the angular
velocity of the ball pivot relative to the joint housing is an indicator
of the wear of the joint. Thus, the quotient forms a wear indicator,
which can also be determined in the motor vehicle, the angular velocity
being able to be determined by differentiation over time of the angle
values determined by the angle measuring device and the two temperature
values being able to be detected by the temperature sensors.

[0007]The course of the frictional heat flux generated by a motion of the
ball pivot relative to the housing can be determined or at least
estimated, and the temperature sensors are preferably seated in different
positions in this frictional heat flux. However, the two temperature
sensors have, in particular, different distances from the center of the
joint ball or a spherical bearing surface of the housing or ball shell.

[0008]The temperature sensors may be arranged in or on the ball shell
and/or in or on the wall of the housing. However, the two temperature
sensors are preferably seated on a plate or printed circuit board
arranged in or on the joint housing and are provided, in particular, on
mutually opposite sides of this plate or printed circuit board.

[0009]The housing has an opening, through which the ball pivot extends,
the area of the housing located opposite the opening preferably
comprising a bottom, on which, e.g., the ball shell is supported. The
temperature sensors are arranged especially in the area of the bottom, so
that the plate or printed circuit board is preferably also seated in the
area of the bottom. Furthermore, the bottom may have an opening, which is
closed by a cover, by which the plate or printed circuit board is held or
formed.

[0010]The angle measuring device is preferably designed as a magnetic
angle measuring device and has a magnet with a magnetic field-sensitive
sensor cooperating with this. The magnet may be designed as a permanent
magnet or the magnetic field-sensitive sensor may be designed as a
magnetoresistive sensor or as a Hall effect sensor. In particular, the
magnet is fastened to the ball pivot and the magnetic field-sensitive
sensor to the housing. However, a reversed arrangement is possible as
well.

[0011]Furthermore, the angle measuring device is connected especially at
least indirectly to the ball and socket joint and may be arranged outside
same. However, the angle measuring device is preferably provided in or on
the ball and socket joint or the ball and socket joint housing and is
especially integrated in the ball and socket joint. Thus, a highly
compact measuring set-up can be obtained, on the whole, which is
protected by the joint housing and optionally by the cover from external
effects.

[0012]Upon closer examination, a force exerted by the ball pivot on the
joint housing or on the ball shell may be additionally included in the
wear indicator. It was found, in particular, that the above-mentioned
quotient can be formed by dividing the temperature difference by the
product of the angular velocity and this force. The force exerted by the
ball pivot on the joint housing or on the ball shell can therefore
preferably be determined by at least one force sensor.

[0013]The measurement of the angle is, however, more important than the
measurement of the force. If the ball and socket joint is arranged in the
wheel suspension of a motor vehicle, the force can also be estimated from
the weight of the vehicle and the extent of jouncing, which can be
determined from the measured angle. Thus, the angle measuring device can
also be used as a force sensor. It is even possible to assume or set the
force as a constant in the simplest case.

[0014]The force sensor is connected especially at least indirectly to the
ball and socket joint and may be arranged outside same. However, the
force sensor is preferably provided in or on the ball and socket joint or
the ball and socket joint housing, and it is especially integrated in the
ball and socket joint. Furthermore, the force sensor may be formed by a
piezoelectric sensor.

[0015]To determine the wear indicator, the two temperature sensors, the
angle measuring device and optionally the force sensor are preferably
provided with an analyzing means, by which the wear indicator
characterizing the wear of the ball and socket joint can be determined.
The analyzing means has, in particular, a differentiator, which is
connected to the angle measuring device; a difference former connected to
the two temperature sensors, and a calculating unit, which is arranged
downstream of the differentiator and the difference former and is
optionally connected to the force sensor, wherein the difference former
may be designed as a differential amplifier. The calculating unit may
comprise at least one (first) divider and preferably additionally has a
multiplier and/or a second divider.

[0016]The analyzing means may be designed by means of analog or digital
assembly units. However, the analyzing means is preferably formed by at
least one digital computer, in which a program is stored, by means of
which the signals measured by the angle measuring device, the temperature
sensors and optionally the force sensor can be processed to determine the
wear indicator.

[0017]The present invention also pertains to a motor vehicle with a
vehicle body, with a motor vehicle component connected to the vehicle
body and with at least one ball and socket joint according to the present
invention, which is connected to the motor vehicle component. The ball
and socket joint may be varied according to all the aforementioned
embodiments. The motor vehicle component is preferably formed by a
chassis component, such as a track rod, or a control arm, especially by
an upper or lower suspension arm.

[0018]The present invention pertains, furthermore, to a process for
determining a wear indicator characterizing the wear of a ball and socket
joint having a joint housing and a ball pivot mounted rotatably and
pivotably in this and/or to the use of the ball and socket joint
according to the present invention for determining the wear indicator by
[0019]determining angle data by consecutive measurement of the angle
between the ball pivot and the joint housing, [0020]determining an
(angular) velocity by differentiating the angle data over time, measuring
temperatures at least two different sites in or on the ball and socket
joint, and [0021]determining the wear indicator on the basis of the
angular velocity and the temperature values.

[0022]The ball and socket joint may be varied according to all the
above-mentioned embodiments. The term "data" shall refer here to the
preferred use of a digital computer for carrying out the process.
However, it is possible that the term "data" designates one or more
values that are available as analog or digital signals, without a
computer being used.

[0023]The wear indicator is preferably also multiplied by a joint-specific
constant and divided by the radius of the joint ball.

[0024]In particular, a force exerted by the ball pivot on the joint
housing or on a ball shell arranged between this and the joint housing is
measured and the wear indicator is additionally determined on the basis
of the measured force.

[0025]Since the ball shell is usually received and held by the joint
housing, the force exerted by the ball pivot on the joint housing
corresponds essentially to the force exerted by the ball pivot on the
ball shell and can be derived from this.

[0026]It is possible, in principle, to modify the angle, the angle data,
the angular velocity, optionally the force, the temperature values, the
difference and/or the wear indicator with suitable factors, and
additional assembly units may be provided for this. If the analyzing
means is formed by a digital computer, these additional assembly units
may also be embodied by means of the digital computer, for which only a
modification of the software is necessary.

[0027]The present invention will be described below on the basis of a
preferred embodiment with reference to the drawings. The various features
of novelty which characterize the invention are pointed out with
particularity in the claims annexed to and forming a part of this
disclosure. For a better understanding of the invention, its operating
advantages and specific objects attained by its uses, reference is made
to the accompanying drawings and descriptive matter in which preferred
embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]In the drawings:

[0029]FIG. 1 is a sectional view of an embodiment of the ball and socket
joint according to the present invention;

[0030]FIG. 2 is a schematic view of the embodiment according to FIG. 1 in
the deflected state;

[0031]FIG. 3 is a schematic view of the embodiment according to FIG. 1 in
a non-worn state;

[0032]FIG. 4 is a schematic block diagram of an analyzing means for the
embodiment according to FIG. 1;

[0033]FIG. 5 is a schematic view of the embodiment according to FIG. 1 in
a worn state; and

[0034]FIG. 6 is a schematic view of a wheel suspension for a motor vehicle
with a ball and socket joint according to the embodiment shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035]Referring to the drawings in particular, FIG. 1 shows an embodiment
of a ball and socket joint 1 according to the present invention, which
has a ball and socket joint housing 2 and a ball pivot 5 comprising a pin
3 and a joint ball 4 connected to this. A ball shell 7, which has a
spherical bearing surface 6 (see FIG. 3) and in which the ball pivot 5
with its joint ball 4 is mounted rotatably and pivotably, is arranged in
the joint housing 2. The ball and socket joint housing 2 has an opening
8, through which the ball pivot 5 extends. Furthermore, a sealing bellows
9, which extends up to the ball pivot 5 and is sealingly in contact with
same, is fastened in the area of the opening 8.

[0036]On the side located opposite the opening 8, the joint housing 2 has
a bottom 11, which is provided with an opening 10, which opening 10 is
closed by a cover 12. The cover 12 comprises a ring-shaped bracket 13,
which is fastened to the joint housing 2 and carries a printed circuit
board 14, on which two temperature sensors 15 and 16 are seated, the
temperature sensor 15 being fastened on a side facing the joint ball 4
and the temperature sensor 16 on a side of the printed circuit board 14
facing away from the joint ball. On the side of the printed circuit board
14 facing away from the joint ball 4, the ring-shaped bracket 13 is
closed with a pourable sealing compound 17, from which an electric line
18, which is connected to the two temperature sensors 15 and 16 and by
means of which the two temperature sensors 15 and 16 are connected to an
analyzing means 19 (see FIG. 4), is lead out.

[0037]A magnet 20, which cooperates with a magnetic field-sensitive sensor
21 arranged on the printed circuit board 14, is arranged in the joint
ball 4, the sensor 21 forming, together with the magnet 20, an angle
measuring device, by means of which a twisting and/or pivoting angle
φ (see FIG. 2) of the ball pivot 5 relative to the joint housing 2
can be detected. The magnetic field-sensitive sensor 21 is connected to
the analyzing means 19 via the electric line 18.

[0038]A force sensor 29, which can determine the force F (see FIG. 3),
which is exerted by the ball pivot 5 on the housing 2 or on the ball
shell 7 and which is measured preferably in or in parallel to the
direction of the longitudinal axis 23 (see FIG. 2) of the housing 2, is
provided between the ball shell 7 and the housing 2 or the bottom 11. The
force sensor 29 is connected to the analyzing means 19 via the electric
line 18. As an alternative, the force sensor 29 may also be arranged
between the ball shell 7 and the ball pivot 5 or outside the joint 1, or
it may be eliminated altogether in a simpler embodiment of the ball and
socket joint.

[0039]FIG. 2 schematically shows the angle φ between the longitudinal
axis 22 of the ball pivot 5 and the longitudinal axis 23 of the joint
housing 2. As an alternative or in addition, it is possible that the
measured angle φ represents the twisting of the ball pivot 5 in
relation to the joint housing 2 about its longitudinal axis 22.

[0040]FIG. 3 shows a schematic view of the non-worn ball and socket joint
1, where the force F is exerted by the ball pivot 5 on the ball shell 7
in an area or point P of the highest load in the loaded state of the ball
and socket joint 1. Component Fn of the force F is directed especially at
right angles to the spherical bearing surface 6 of the ball shell 7 and
forms an angle α with the force F. The force component Fn
designated as the normal force is preferably located on a straight line,
which passes through the center M of the spherical bearing surface 6
having the center M. The center M is, in particular, also the center of
the joint ball 4 and the radius R is also the radius thereof (of the
joint ball).

[0041]A process, by means of which a value characterizing the wear of the
ball and socket joint 1 can be determined, will be described below. The
amount of heat q produced in the joint by friction increases due to
hardening of the lubricating grease introduced into the ball and socket
joint housing 2 and/or due to wear of the ball shell 7. An increased
amount of heat q is an indicator of increased wear, and the amount of
heat q generated by friction is eliminated, among other things, via the
printed circuit board 14 installed in the joint. By measuring the
temperature T2 above the printed circuit board 14 by means of the
temperature sensor 16 and the temperature T1 below the printed circuit
board 14 by means of the temperature sensor 15, the heat flux flowing
through the printed circuit board 14 can be calculated as:

=k1ΔT, with ΔT=(T2-T1).

Here,

[0042]is the derivative of the amount of heat over time, [0043]ΔT is
the temperature difference between the top side and the underside of the
printed circuit board 14, and K1 is a joint-specific constant. On the
other hand, the friction output produced in the joint can be calculated
as

[0043] q . = Fr s t

in which Fr designates the frictional force, s the friction and t the
time. The frictional force Fr is equal here to the product of the normal
force Fn and the coefficient of friction μ, and

Fn = F cos α , with Fr = μ Fn

applies to the normal force Fn.

[0044]In particular, the normal force Fn may be greater, e.g., because of
notch effects, than the force F, where α is the angle between the
force vector F and the normal force Fn. The quotient of the path s and
the time t corresponds to the velocity of rotation and tilting v of the
ball pivot 5, which velocity is, furthermore, equal to the product of the
angular velocity φ of the ball pivot 5 in relation to the ball shell
7 or the housing 2 and the friction radius Rr, which is formed by the
product of the ball pivot radius R and sin α, so that

v=φRsin α.

applies to the velocity of rotation and tilting v of the ball pivot 5.

With

[0045] v = s t ,

q . = Fr s t = μ F Φ . R tan α

is then obtained for the friction output.

[0046]From this follows:

μ tan α = Δ T K 1 F R
Φ . ,

in which the term μtan α forms a suitable wear indicator for the
ball and socket joint 1.

[0047]However, since the variables K1 and R are joint-dependent constants,
these can also be omitted in the determination of the wear indicator, so
that the value I, with

I = Δ T F Φ . ,

is also a suitable wear indicator for the ball and socket joint 1. In a
simpler variant of the ball and socket joint, the force is assumed to be
a constant and can therefore be omitted in the determination of the wear
indicator. This simplified wear indicator Iv is thus obtained as
follows:

I v = Δ T Φ . .

[0048]The wear indicator μtan α or I can be determined with the
detection of the temperature difference ΔT, the velocity of
rotation {acute over (φ)} of the ball pivot 5 as well as the external
force F. The external force F and/or the velocity of rotation {grave over
(φ)} of the ball pivot 5 can be measured or determined with sensors
arranged outside the joint 1. However, the force sensor 29 and/or the
angle measuring device 20, 21 are preferably arranged in the joint 1 and
are integrated in same.

[0049]If the wear indicator μtan α or I exceeds a preset
threshold value, the ball and socket joint 1 should be checked more
closely and possibly replaced. If the angle α is also measured by
means of suitable sensors in case of a favorable ball and socket joint
design, it is, furthermore, possible to make a distinction between the
hardening of the grease (change in μ) and wear of the shell (change in
α).

[0050]FIG. 4 shows a schematic block diagram of the analyzing means 19,
where a difference former 24 is connected to the two temperature sensors
15 and 16 and yields the temperature difference ΔT as an output
signal. A differentiator 25 is connected to the angle measuring device or
to the magnetic field-sensitive sensor 21 and yields the angular velocity
{grave over (φ)} as the output signal. The difference former 24 and
the differentiator 25 are followed downstream by a calculating unit 47,
which is connected to the force sensor 29 and which yields the wear
indicator I as the output signal. In addition, it is possible to multiply
the value I by K1 and divide by R in order to obtain the term μtan
α.

[0051]According to FIG. 4, the calculating unit 47 has a multiplier 26,
which is arranged downstream of the differentiator 25, is connected to
the force sensor 29 and yields the product {acute over (φ)}F as an
output variable. The calculating unit 47 has, furthermore, a divider 30,
which is arranged downstream of the multiplier 26 and the difference
former 24 and yields the value I as an output signal.

[0052]The wear indicator I or μtan α determined may be sent to a
threshold value transducer 27, which is formed by the analyzing means 19
here and by which a signal transmitter 28 arranged downstream of this
threshold value transducer can be actuated. The signal transmitter 28,
which is arranged especially in the passenger compartment of a vehicle 37
(see FIG. 6), may be designed as an audio or visual signal transmitter in
order to inform the driver of the wear of the ball and socket joint 1 in
case the permissible wear or the threshold value is exceeded. For
example, a light is suitable for use as a visual signal transmitter. It
is possible as an alternative that the wear value I or μtan α or
the output signal of the threshold value transducer 27 is sent to a
vehicle control. Since the angular velocity {grave over (φ)} may have
different signs depending on the direction of rotation or pivoting of the
ball pivot 5, it is possible to provide an absolute value transducer,
which is arranged, e.g., downstream of the calculating unit 47 and is
optionally arranged upstream of the threshold value transducer. The
absolute value transducer sends as the output signal the (absolute) value
of the signal sent to it and may also be provided between the
differentiator 25 and the calculating unit 47 or integrated in these.
Furthermore, it is possible to calculate the temperature difference
ΔT with ΔT=(T1-T2).

[0053]FIG. 4 shows only an example of the analyzing means 19, which shall
not be interpreted as a limiting example. In particular, the combination
of the multiplier 26 and the divider 30 may be replaced by an equivalent
assembly unit or calculating unit, which comprises, e.g., two consecutive
dividers. Even though it is possible to build up the analyzing means 19
from analog or digital assembly units, the analyzing means 19 is formed
especially by a digital computer or by a software running in this
according to the embodiment, in which case the wear indicator I or
μtan α is calculated numerically or determined from the signals
T1, T2, φ and F (optionally with the constants K1 and R).

[0054]FIG. 5 shows a schematic view of the ball and socket joint 1 in the
worn state, where wear is associated with a change in the angle α.
The area or point P of the highest load thus migrates with increasing
wear of the ball and socket joint 1. The area or point P migrates
practically only slightly, so that the view according to FIG. 5 should be
considered to be only schematic to illustrate this migration.

[0055]While the area or point P can still be determined or calculated in a
testing field in the non-worn state (see FIG. 3), additional sensors may
be provided in the ball and socket joint 1 in the worn state (see FIG. 5)
for the accurate determination of the area or point P. For example, a
plurality of force sensors or a force sensor array 46 formed by these may
be arranged in the joint housing 2 or in the ball shell 7 and they can
detect the area or point P. However, this is necessary only when higher
accuracy is required for the determination of the wear value I or μtan
α. Distinction can also be made in this case between wear of the
shell and hardening of the grease.

[0056]An incipient wear and/or an incipient hardening of the grease can be
recognized early by the measurement of the "wear indicator." Damage to
the ball and socket joint 1 is detected early, before failure and
situations that are critical for safety develop. The electronic system
and the temperature sensors can be fully protected against harmful
substances and they can be combined with other sensors.

[0057]FIG. 6 shows a schematic view of a wheel suspension 31, where a
wheel carrier 32 is connected to a vehicle body 36 of the motor vehicle
37, which is shown partially, via an upper suspension arm 33, a lower
suspension arm 34, and a radius arm 35. The upper suspension arm 33 is
connected to the wheel carrier 32 via the ball and socket joint 1
according to the present invention and to the vehicle body 36 via a joint
or elastomer bearing 38. The lower suspension arm 34 is connected to the
wheel carrier 32 via a ball and socket joint 39 and to the vehicle body
36 via an elastomer bearing 40. Furthermore, the radius arm 35 is
connected to the wheel carrier 32 via a ball and socket joint 41 and to
the vehicle body 36 via an elastomer bearing 42. A tire or wheel 43,
which is in contact with a road surface 45, shown schematically, in a
wheel contact point 44, is mounted rotatably on the wheel carrier 32.
Furthermore, an analyzing means 19 is arranged in the vehicle body 36.

[0058]Wear measurement of the ball and socket joint 1 is carried out in
the wheel suspension 31 being shown. In addition or as an alternative, it
is possible to carry out such a measurement for one or more of the other
ball and socket joints of the wheel suspension 31 as well.

[0059]While specific embodiments of the invention have been shown and
described in detail to illustrate the application of the principles of
the invention, it will be understood that the invention may be embodied
otherwise without departing from such principles.